The present invention relates to a pre-compression pump for dispensing metered quantities of fluid, and, more generally, to a pre-compression pump in which the fluid is dispensed independently of the actuating force exerted on the pump by the user.
Documents WO 87/04373 and EP-0 265 270 disclose pumps of this type. When the pump is actuated, a spring is compressed under the effect of the pressure generated inside the pump chamber, said spring being released at the end of the actuating stroke, after an outlet valve has opened, so that the metered quantity of fluid contained in the pump chamber is expelled by said spring, independently of the actuating force of the user.
In order to ensure that this type of device operates reliably, the outlet valve of the pump chamber must guarantee that the pump chamber is closed off in totally-leaktight manner throughout the entire actuating stroke of the pump, and can open only at the very end of the actuating stroke of said pump, so as to enable the fluid to be expelled. In the above-mentioned documents of the state of the art, the outlet valve is made in the form of an elastically-deformable sleeve disposed between the pump body and the moving actuating rod of the pump. The valve must be stiff enough so that it is not deformed while the pump is being actuated, under the effect of the pressure generated in the pump chamber. It opens by being deformed elastically at the end of the actuating stroke, by means of a shoulder formed in the pump body. That type of valve member suffers from the drawback that it must be both stiff enough not to be deformed before the end of the stroke of the pump, and also deformable enough so that, at the end of the actuating stroke, it can be deformed without having to apply too much force, under the effect of a mechanical cam. It is difficult to strike a satisfactory balance between these two contradictory requirements, and said outlet valve can cause the pump to operate unreliably. In particular, the slightest differences in size or stiffness due to the manufacturing tolerances of the outlet valve can cause such a malfunction.
An object of the present invention is to provide a pre-compression pump, in particular a pre-compression pump in which the fluid is dispensed independently of the actuating force of the user, and that does not reproduce the above-mentioned drawbacks.
Another object of the invention is to provide such a pre-compression pump that is simple and easy to manufacture and to assemble, and that is reliable to use.
Another object of the present invention is to provide such a pre-compression pump that guarantees that the contents of the pump chamber are dispensed totally and reproducibly each time the pump is actuated, independently of the actuating force of the user.
The present invention thus provides a pre-compression pump for dispensing metered quantities of fluid, said pump including a piston secured to or integral with an actuating rod and slidably-received in a pump body including a pump chamber defined between an inlet valve and an outlet valve, said pre-compression pump being characterized in that, when the pump is actuated, said outlet valve is urged towards its closed position by the pressure of the fluid contained in the pump chamber, and in that, at the end of the actuating stroke of the pump, a lever element moves said outlet valve towards its open position to enable the fluid contained in the pump chamber to be expelled.
Thus, unlike in the prior art devices, the outlet valve of the pump of the present invention does not have to withstand the pressure of the fluid throughout the entire actuating stroke of the pump, but rather it is urged towards its closed position by the fluid contained in the pump chamber. There is therefore no risk of the outlet valve opening early. In addition, because the outlet valve is urged towards its closed position by the pressure of the fluid contained in the pump chamber, it does not have to be made with a predetermined stiffness, and it is easy for a lever element to open it at the end of the actuating stroke without having to overcome resistance to deformation inherent to the material of the outlet valve, as is necessary in the prior art devices.
Advantageously, said lever element is mounted to slide with said piston and said outlet valve to reach a cam member which is secured to or integral with the pump body and which, at the end of the actuating stroke of the pump, deforms and/or displaces the lever element so as to open the outlet valve.
Advantageously, said cam member is formed by a shoulder in the pump body.
In a first advantageous variant embodiment of the present invention, said lever element is made integrally with said outlet valve.
In a second advantageous variant embodiment of the present invention, said lever element is made separately from said outlet valve.
Preferably, when the pump is in the rest position, said inlet valve is urged towards its open position by a spring, and, when the pump is actuated, said inlet valve is urged towards its closed position and moves by compressing the spring under the effect of the pressure of the fluid contained in the pump chamber, said spring being released suddenly when the outlet valve opens at the end of the actuating stroke of the pump, thereby bringing the inlet valve back towards its rest position and expelling the fluid contained in the pump chamber independently of the actuating force exerted on the pump by the user.
Advantageously, said spring of the inlet valve also returns the piston to its rest position.
Advantageously, said inlet valve is made in the form of a hollow cylinder closed at one end by an end wall, the edge of the open end of said hollow cylinder co-operating, as of the beginning of the actuating stroke of the pump, with a cylinder of the pump body to close the inlet valve, the spring bearing at one end against the end wall of the inlet valve and at its other end against a portion of the pump body.
The present invention also provides a fluid dispenser device, characterized in that it includes such a pre-compression pump.